The coronal aorto-mesenteric orientation theory for post-operative nausea and vomiting following scoliosis surgery in children: a pilot study.

Background: Post-operative nausea and vomiting (PONV) is often encountered following corrective scoliosis surgery in children, frequently attributed to high-dose opiate administration. PONV is a frequent cause of prolonged hospital stay. Mechanisms related to transient partial duodenal compression by narrow angulation of the superior mesenteric artery (SMA) and aorta following scoliosis surgery are poorly understood and might be implicated in PONV. This study investigates relationships between biomechanical anatomic variations of the SMA and aorta, and its relationship with clinically significant PONV following scoliosis surgery in children.

Methods: Children undergoing elective spinal arthrodesis for adolescent idiopathic scoliosis were assessed by preoperative abdominal ultrasound and spinal X-ray prior to surgery. Post-operative assessment of clinically significant PONV is compared to preoperative imaging and clinical variables.

Results: Thirteen patients (11 female and two male), with a mean age of 14 years and 1 month were included. Five patients (38.5%) developed clinically significant PONV. A significant association was observed between the coronal aorto-mesenteric orientation and PONV (P = 0.035). Of the five patients who developed PONV, two had direct coronal angulation of the SMA, one had left angulation and two had right angulation. Patients with significant PONV had narrower aorto-mesenteric distances which approached significance (P = 0.06). No other preoperative variable reached significance.

Conclusion: Patients with coronal aorto-mesenteric orientation preoperatively appear at greater risk of developing significant PONV following scoliosis surgery, independent of opiate requirements, prompting consideration of transient partial duodenal obstruction as an important factor in the mechanisms of PONV. A coronal aorto-mesenteric orientation theory (CAMOT) is proposed to explain this biomechanical vascular 'scissor'.